CT Virtual Endoscopy in Assessing Ossicular Chain Disruption Csused by Temporal Bone Fracture and Ear Trauma

Abstract

ObjectiveTo explore the value of computed tomography virtual endoscopy (VE) in assessing ossicular chain disruption in temporal bone fracture and ear trauma with intact tympanum. MethodsHigh resolution spiral computerized tomography (CT) was completed in 35 cases of temporal bone fracture and 5 cases of tympanum trauma, all with intact or healed tympanum. Three-dimensional reconstruction was completed using a virtual endoscopy software. Audiological tests were conducted in all patients and evaluation of facial nerve injury in patients with facial paralysis. Patients with mild conductive deafness, ossicular chain subluxation on VE, and no facial paralysis were treated conservatively for 4-12 weeks with repeated hearing evaluation; those with facial paralysis underwent surgery if no recovery after 4-8 weeks of conservative treatment. Patients with moderate to severe conductive hearing loss or mixed hearing loss, incus long process fracture or dislocation on VE and facial paralysis, underwent ossicular chain reconstruction and facial nerve decompression after conservative treatment for 4-8 weeks, or exploratory tympanotomy only if no facial paralysis. VE, audiological tests and facial nerve function tests were repeated in 3-6 months after surgery. ResultsOf the 6 cases with mild conductive hearing loss, ossicular chain subluxation and no facial paralysis, 3 recovered to normal hearing spontaneously and 3 showed no significant improvement, after 4-12 weeks of conservative treatment. After conservative treatment for 4-8 weeks, 3 of the 12 cases with mild conductive deafness, ossicular chain dislocation on VE and facial paralysis recovered to normal hearing and House-Brackmann (HB) grade I facial function from HB grade II, 4 showed facial function recovery to HB grade I (n=2) or II (n=2) from HB grade III but no hearing recovery, and 5 gained no recovery and went on to receive exploratory tympanotomy and facial nerve decompression. The 11 cases with moderate to severe conductive deafness, incus long process fracture or dislocation on VE and facial paralysis all received ossicular chain reconstruction and facial nerve decompression after 4-8 weeks of conservative treatment. The 7 cases with moderate to severe conductive deafness, dislocated or fallen incus on VE but no facial paralysis received ossicular chain reconstruction after conservative treatment. The 4 cases with mixed hearing loss, dislocated or fallen incus on VE and no facial paralysis received ossicular chain repair via the intact canal wall epitympanum approach after conservative treatment. Pharmacological therapies continued postoperatively in these patients to treat sensorineural deafness. Although temporal bone CT scans displayed the fracture line and malleus/incus abnormalities, VE provided additional detailed information on dislocation of incudomalleal and incudostapedial joints, incus dislocation or fracture, separation between crus longum incudis and stapes, and incus shifting. These were all confirmed during surgery. VE results and surgery findings were 100% consistent in patients with ossicular chain disruption. ConclusionVE can provide reliable visual evidence for accurate assessment of traumatic ossicular chain disruption, timing of surgery and individualizing surgical strategies and postoperative follow-up.